The Professor's Cube

VIII. Solve the Bottom Outer Edges


Sorry to say but hands down, this is the most confusing part of the solution. If you can guide your way out of this section, then the rest will just be a walk through the park.

The remaining 8 outer-edges are already on the bottom layer, and chances are they are pretty much scrambled. The first step is to arrange them in the correct positions. Randomly choose a front side, and proceed to solve the back edges; starting with the back-left edge first and the back-right edge second.

Note: these diagrams look strange. The first one appears to take 4 outer-edges and cram them into one. What the first diagram actually means is that if an outer-edge cube is coming from the left or right sides, then you must repeat the sequence until it appears in the back-left edge. You may have to repeat this sequence four times before that happens.

The second diagram represents any outer-edge from the front side moving to the back-left edge. You may have to repeat that squence twice before it lands there. The dark squares on both diagrams are edges cubes that do not move at all during the process.


Now continue to...

~~~~ Move an Outer-Edge to the Back-Left ~~~~

______________________________

Move an edge
from either side

    

Repeat the
sequence:

    

...until the edge lands
on the back-left

    

M- B- M+ B2
M- B- M+

    

You may have to
repeat the sequence
as many as 4 times.

Bottom View

______________________________

Move an edge
from the front

  

Repeat the
sequence:

    

...until the edge lands
on the back-left

    

M- B2 M+ B-
M- B- M+
O- B2 O+ B+
O- B+ O+

    

You may have to
repeat the sequence
as many as 2 times.

Bottom View


Now continue to...

~~~~ Move an Outer-Edge to the Back-Right: ~~~~

______________________________

Move an edge
from either side

    

Repeat the
sequence:

    

...until the edge lands
on the back-right

    

O- B+ O+ B2
O- B+ O+

    

You may have to
repeat the sequence
as many as 4 times.

Bottom View

______________________________

Move an edge
from the front

    

Repeat the
sequence:

    

...until the edge lands
on the back-right

    

O- B2 O+ B+
O- B+ O+
M- B2 M+ B-
M- B- M+

    

You may have to
repeat the sequence
as many as 2 times.

Bottom View


If you are lucky, the outer-edges going to the back are already paired. You can still move them one at a time, or you can use these shortcuts:

~~~~ Move an Edge-Pair ~~~~

...from the left:

    

...from the front:

    

...from the right:

    
    

Bottom View

Bottom View

Bottom View

O- B+ O+ B2
O- B+ O+
M- B- M+ B2
M- B- M+

    

M- M- B2
M- M- B2
M- M-

    

M- B- M+ B2
M- B- M+
O- B+ O+ B2
O- B+ O+

All sequences only have to be performed once to accomplish the move.


Both back edges should now be in place...

  
  

...rotate the entire puzzle so that the fixed edges are in the front...

  
  

...and solve the "other" back side.

Once again, you have to use the same sequences as before, except this time, the outer-edges are coming from the sides only.

Move a single
edge to the
back-left:

  

Move a single
edge to the
back-right:

  

Swap the left
pair of edges
with the back
pair of edges:

  

Swap the right
pair of edges
with the back
pair of edges:

  
  
  

Bottom View

Bottom View

Bottom View

Bottom View

M- B- M+ B2
M- B- M+

(4 times max.)

  

O- B+ O+ B2
O- B+ O+

(4 times max.)

  

O- B+ O+ B2
O- B+ O+
M- B- M+ B2
M- B- M+

(1 time only)

  

M- B- M+ B2
M- B- M+
O- B+ O+ B2
O- B+ O+

(1 time only)


The back and front edges are now in place....

  
  

...rotate the entire puzzle so that the fixed edges are on the sides...

  
  

...and solve the back side again.

This time, you only have to use the sequences that move the outer-edges from the front to the back:

Move a single
edge to the
back-left:

    

Move a single
edge to the
back-right:

    

Swap the front
pair of edges
with the back
pair of edges:

    
    

M- B2 M+ B-
M- B- M+
O- B2 O+ B+
O- B+ O+

(2 times max.)

  

O- B2 O+ B+
O- B+ O+
M- B2 M+ B-
M- B- M+

(2 times max.)

    

M- M- B2
M- M- B2
M- M-

(1 time only)

    

Once you solve the back side (for the third time), the remaining 2 outer-edges are forced to the front side, where they belong! Therefore, all 8 bottom outer-edges are in place. Now for the next step: INVERSION.


Inversion

There are 5 different inversion schemes:

  1. Invert 2 outer-edge pairs on adjacent sides
  2. Invert 2 outer-edge pairs on opposite sides
  3. Invert 4 outer-edge pairs
  4. Invert 3 outer-edge pairs
  5. Invert 1 outer-edge pair

For each inversion scheme, you must rotate the entire puzzle so that the inverted edge-pairs are positioned exactly like the ones in the diagrams, before attempting the sequence of moves!

~~~~ Case #1: Invert two adjacent edge-pairs ~~~~

    

[MNO]- B- [MNO]+ B-
[MNO]- B2 [MNO]+ B2
[MNO]- B- [MNO]+ B-
[MNO]- B2 [MNO]+ B2

    

Result:

The bottom
outer-edges
are solved.

______________________________

~~~~ Case #2: Invert two opposite edge-pairs ~~~~

    

[MNO]- B- [MNO]+ B-
[MNO]- B2 [MNO]+ B2
[MNO]- B- [MNO]+ B-
[MNO]- B2 [MNO]+ B2

    

Result:

Two adjacent edge-pairs
are still inverted.
Go back to Case #1,
do the sequence, and the
bottom edges are solved.

______________________________

~~~~ Case #3: Invert four edge-pairs ~~~~

    

[MNO]- B- [MNO]+ B-
[MNO]- B2 [MNO]+ B2
[MNO]- B- [MNO]+ B-
[MNO]- B2 [MNO]+ B2

    

Result:

Two adjacent edge-pairs
are still inverted.
Go back to Case #1,
do the sequence, and the
bottom edges are solved.

______________________________

~~~~ Case #4: Invert three edge-pairs ~~~~

    

M- B- M- B2
M- B2 M+ B+ M+
O- B- O- B2
O- B2 O+ B+ O+
M- B- M- B2
M- B2 M+ B+ M+

    

Result:

The bottom
outer-edges
are solved.

______________________________

~~~~ Case #5: Invert one edge-pair ~~~~

    

M- B- M- B2
M- B2 M+ B+ M+
O- B- O- B2
O- B2 O+ B+ O+
M- B- M- B2
M- B2 M+ B+ M+

    

Result:

Two adjacent edge-pairs
are still inverted.
Go back to Case #1,
do the sequence, and the
bottom edges are solved.


As it turns out, only two different sequences were used throughout all five cases.
Now that the bottom outer-edges are solved, the next thing to tackle are the
Bottom Inner-Edges.


@ Notation / Top Face
@ Top Corners @ Top Outer-Edges @ Top Inner-Edges
@ Middle Outer-Edges @ Middle Inner-Edges
@ Bottom Corners @ Bottom Outer-Edges @ Bottom Inner-Edges
@ Middle & Bottom Faces

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